The present invention relates to a multipole low-voltage circuit breaker with an insulating material housing and one arc quenching chamber for each pole comprising quenching baffles. Such a circuit breaker has become known, for instance, through U.S. Pat. No. 4,540,961. The quenching baffles of a quenching chamber form a block which is held together by insulating parts and can be inserted into the quenching chamber. An example of the arrangement of the insulating parts can be seen from U.S. Pat. No. 4,247,746. It is also known to use, for holding together the quenching baffles, insulating materials which are decomposed under the influence of the heat of the switching arc, forming gas, and thereby promoting the quenching of the arc.